This application relates to U.S. applications Ser. No. 255,650, filed Oct. 11, 1988, and continuation-in-part application Ser. No. 467,742, and application Ser. No. 467,724, both filed Jan. 19, 1990.
1. Field of the Invention
As do the other applications referenced above, the present invention relates to the replacement of pre-placed prosthetic joints and more particularly to a method and apparatus for removing the cement mantle used to secure the pre-placed joint in place.
The replacement of a failed prosthetic joint, such as a hip or knee joint, requires that both the prosthetic appliance and the cement mantle holding it in place within the bone cavity be removed. The old prosthetic device is usually easily removed using a slap-hammer, since its surface is smooth and separable from the underlying cement mantle. The cement mantle, however, is tightly adherent to the surrounding bone and generally remains so adhered, even after the prosthetic device is removed.
2. Description of the Relevant Art
In the prior art, removal of the adhered cement mantle was performed by chipping the mantle away with a hammer and chisel. This and related methods are tedious and allow the possibility of fracturing the underlying bone.
Methylmethacrylate cement is the most accepted type of cement used to secure prosthetic joint appliances to bone. Old hardened methylmethacrylate cement is capable of being partially dissolved and softened by the application of new like fluid cement thereto. The resulting composite of old and new cement cures into an integral bonded composite in a matter of minutes.
In the method of the invention described in application Ser. No. 255,650, a mass of new fluid methylmethacrylate cement is placed in contact with the hardened mantle of old methylmethacrylate cement desired to be removed. A pulling appliance is then imbedded within the fluid cement and the mass of cement is permitted to cure and harden, thus forming a bond between the appliance and the mantle of old cement. Tension is then applied to the pulling mantle to pull the appliance and the entire bonded mantle from the bone.
However, even in that method, the force needed to pull the entire mantle from the bone may damage the bone. Continuation-in-part application Ser. No. 467,742 concerns the improvement or removing the bonded mantle from the bone in a number of pieces to reduce the amount of force needed to remove each piece to avoid such damage to the surrounding bone.
Application Ser. No. 467,724 involves a kit of components for use with the method of removing the mantle in pieces, to simplify the procedure and make it essentially foolproof.